U.S. patent application number 11/985303 was filed with the patent office on 2008-05-15 for brush holder.
Invention is credited to Torsten Tussing.
Application Number | 20080111442 11/985303 |
Document ID | / |
Family ID | 39277397 |
Filed Date | 2008-05-15 |
United States Patent
Application |
20080111442 |
Kind Code |
A1 |
Tussing; Torsten |
May 15, 2008 |
Brush holder
Abstract
A brush holder (2) has a carbon holder (4) which forms a guide
(12) for a carbon brush (6) and at which there is provided a spring
arrangement that applies a contact spring force (KF) to the carbon
brush (6) along the guide (12) and, at the same time, presses the
carbon brush (6) into a taper (23) of the guide (12) with a
supporting spring force (SF), with the spring arrangement having a
contact spring (8) for generating the contact spring force (KF) and
a supporting spring (28) which is separate from the latter and
which generates the supporting spring force (SF).
Inventors: |
Tussing; Torsten; (Koengen,
DE) |
Correspondence
Address: |
ABELMAN, FRAYNE & SCHWAB
666 THIRD AVENUE, 10TH FLOOR
NEW YORK
NY
10017
US
|
Family ID: |
39277397 |
Appl. No.: |
11/985303 |
Filed: |
November 13, 2007 |
Current U.S.
Class: |
310/242 |
Current CPC
Class: |
H01R 39/415
20130101 |
Class at
Publication: |
310/242 |
International
Class: |
H01R 39/44 20060101
H01R039/44; H01R 39/41 20060101 H01R039/41 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 14, 2006 |
DE |
10 2006 035 440.0 |
Claims
1. A brush holder (2), comprising a carbon holder (4) which forms a
guide (12) for a carbon brush (6), and spring means for applying a
contact spring force (KF) to the carbon brush (6) along the guide
(12) and for simultaneously pressing the carbon brush (6) into a
taper of the guide (12) by a supporting spring force (SF), the
spring means having a contact spring (8) for generating the contact
spring force (KF) and a supporting spring (28) for generating the
supporting spring force (SF) and separate from the contact
spring.
2. A brush holder according to claim 1, wherein the taper is formed
by a guide surface (16) at a first guide side (14) of the guide
(12) and by an adjacent, second guide side (22), and wherein the
guide surface (16) and the second guide side (22) enclose an acute
angle (w).
3. A brush holder according to claim 2, wherein the guide (12) at
the first guide side (14) is delimited exclusively by the inclined
guide surface (16).
4. A brush holder according to claim 1, wherein the guide (12) is
delimited exclusively by the supporting spring (28) at a third
guide side (24) located opposite the taper.
5. A brush holder according to claim 4, wherein the supporting
spring (28) is formed by a leaf spring.
6. A brush holder according to claim 5, wherein the supporting
spring (28) has a clamping portion (30) located between a carrier
(3) of the brush holder (2) and the carbon holder (4) and having an
application portion (26) which projects into the carbon holder (4)
and forms the third guide side (24).
7. A brush holder according to claim 6, wherein the application
portion (26) makes contact over a length (IB) amounting to at least
80% of a length (IF) of the guide surface (16).
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The invention is directed to a brush holder having a carbon
holder which forms a guide for carbon brushes, spring means
provided at the carbon holder for applying a contact spring force
to the carbon brush along a guide axis of the guide. At the same
time, the spring means biases the carbon brush transverse to the
guide axis into a taper of the guide with a supporting spring
force, and the carbon brush has a corresponding taper which
cooperates with the taper of the guide.
[0003] 2. Description of the Prior Art
[0004] In brush holders of the type mentioned above, the carbon
brushes are held in the carbon holders in a relatively stable
manner. The spring means ensures that the carbon brushes are biased
in direction of a commutator and that the carbon brushes are
supported in the carbon holders laterally so as to be substantially
free of play. Possible wear at the side surfaces of the carbon
brushes is compensated in that the carbon brushes are pressed
farther into the tapering area of the guide transverse to the
actual guiding direction.
[0005] German Patent DE 33 46 595 C2 discloses a brush holder for
electric machines which has a carbon holder for guiding a carbon
brush scroll spring means is provided at the carbon holder and
applies pressure to the carbon brush with an inclined application
surface of a pressure sliding piece along the guide and transverse
thereto. The carbon brush is pressed to one side of the carbon
holder on which a taper is formed by two inclined supporting
surfaces.
[0006] The drawback of the known brush holder consists in that the
scroll spring means and the bearing means, which is required for
the latter on the brush holder, are relatively costly to produce.
Accordingly, the costs of producing the brush holder as a whole is
relatively high. In addition, the supporting pressure that can be
generated by the scroll spring means is relatively small so that
strong vibrations can lead to a tilting of the carbon brush in the
carbon holder and, therefore, to accelerated wear in some
areas.
SUMMARY OF THE INVENTION
[0007] It is an object of the present invention to provide a brush
holder in which the drawbacks of a know brush holder are eliminated
and an improved lateral support of the carbon brush is achieved by
using simple spring means.
[0008] This and other objects of the present invention, which will
become apparent hereinafter, are achieved by providing a brush
holder in which the spring means includes a contact spring for
generating a contact spring force and a supporting spring which is
separate from the contact spring and which generates a supporting
spring force. With this functional separation, it is possible to
design the supporting spring that generates the supporting
pressure, independently from the contact spring and in such a way
that a sufficient lateral supporting pressure is applied to the
carbon brush so as to hold it permanently in contact with the
inclined guide surface when strong vibrations occur in operation.
In this way, tilting of the carbon brush and resulting increased
wear in some areas can be reduced to a minimum or completely
eliminated.
[0009] The taper is advantageously formed by a guide surface on a
first guide side of the guide and by an adjacent, second guide
side. The guide surface and the second guide side enclose an acute
angle. In this way, by forming a corresponding taper at the carbon
brush which defines a corner angle substantially corresponding to
the acute angle, a stable support of the carbon brush can be
ensured at all times even after a very long period of operation and
a corresponding lateral wear.
[0010] The guide at the first guide side is advantageously
delimited exclusively by the inclined guide surface. With such a
single inclined guide surface, the production costs for both the
carbon holder and the carbon brush are noticeably reduced. On the
other hand, lateral wear, which occurs at the carbon brush over its
lifetime, can be compensated in an excellent manner in this
way.
[0011] In a particularly preferred embodiment, the guide is
delimited on its third guide side located opposite the first guide
side exclusively by the supporting spring. This makes possible to
apply pressure to the carbon brush in a very uniform manner and
over a maximum surface. In this way, the carbon brush can be
subjected to action of a relatively high supporting spring force
which, in turn, also prevents tilting of the carbon brush in the
carbon holder even with strong vibrations.
[0012] In this connection, it is advantageous when the supporting
spring is formed by a leaf spring to ensure an economical
production of the supporting spring.
[0013] The supporting spring advantageously has a clamping portion
which is clamped between a carrier of the brush holder and the
carbon holder. Further, the supporting spring has an application
portion which projects into the carbon holder and forms the third
guide side. In this way, the supporting spring and its bearing
means at the brush holder can be constructed in a particularly
simple manner which reduces production cost.
[0014] The application portion can preferably contact the carbon
brush over a length amounting to at least 80% of the length of the
guide surface along the guide axis. In this way, the supporting
pressure can be applied over almost the entire length of the guide
so that formation of areas with increased wear can be prevented to
a great extent.
[0015] The novel features of the present invention, which are
considered as characteristic for the invention, are set forth in
the appended claims. The invention itself, however, both as to its
construction and its mode of operation, together with additional
advantages and objects thereof, will be best understood from the
following detailed description of preferred embodiments, when read
with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The drawings show:
[0017] FIG. 1 a perspective view of a brush holder according to the
present invention;
[0018] FIG. 2 a cross-sectional view of a carbon holder of the
brush holder shown in FIG. 1;
[0019] FIG. 3 a longitudinal cross-sectional view of the carbon
holder in plane 3 in FIG. 2; and
[0020] FIG. 4 a longitudinal cross-sectional view of the carbon
holder shown in FIG. 3, with the carbon brush omitted.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0021] FIG. 1 shows a brush holder 2, particularly for a hand-held
power tool, not shown, with a substantially ring-shaped carrier 3
that supports two carbon holders 4. Carbon brushes 6 are guided in
these carbon holders 4, with each carbon brush 6 being biased
against a commutator 10 by a contact spring force KF generated by a
contact spring 8. The contact springs 8 are formed, for example, as
coil springs. For the sake of clarity, only one contact spring 8 is
shown.
[0022] To guide a respective carbon brush 6, each carbon holder 4
forms a substantially four-sided guide 12 along a guide axis A, as
can be seen particularly from FIG. 2. A first guide side 14 remote
from the carrier 3 is substantially formed by a guide surface 16 of
a holder wall 18 which is arranged at an inclination to a second
guide side 22 formed by a holder wall 20, and encloses therewith an
acute angle w. Accordingly, the guide surface 16 together with the
second guide surface 22, forms a taper 23 directed transverse to
the guide axis A.
[0023] As an alternative to delimiting the guide 12 on the first
guide side 14 completely by the inclined guide surface 16, the
first guide side 14 can also be formed only partly by the guide
surface 16, while another part is formed by an area of the holder
wall 18 directed at a right angle to the second guide side 22.
[0024] At a third guide side 24 which faces the carrier 3 and is
located opposite to the first guide side 14, the guide 12 is
delimited exclusively by an application portion 26 of a supporting
spring 28 which projects into the carbon holder 4. This supporting
spring 28 presses the respective carbon brush 6 with a supporting
spring force SF in direction of the first guide side 14 and,
accordingly, into the taper 23. In this way, the carbon brush 6
contacts the first guide side 14 with a first contact surface K1 at
the inclined guide surface 16 and contacts the second guide side 22
with a second contact surface K2 at the holder wall 20. The carbon
brush 6 defines a corner angle e between the two contact surfaces
K1, K2, which corner angle e substantially corresponds to the acute
angle w of the taper 23. Accordingly, the contact surfaces K1, K2
form a taper on the brush side which is adapted to the taper 23 on
the guide side.
[0025] As can be seen from FIG. 3, the supporting spring 28 is
formed as a leaf spring which has a clamping portion 30 at an end
remote from the application portion 26. This clamping portion 30 is
secured between the carrier 3 and a holder bearing wall 32 of the
respective carbon holder 4 facing the carrier 3. The application
portion 26 and the clamping portion 30 are connected to one another
by a tab portion 34 with which the supporting spring force SF can
be produced.
[0026] For this purpose, the tab portion 34 is designed in such a
way that, in an unloaded state according to FIG. 4 in which no
carbon brush 6 is arranged in the carbon holder 4, the supporting
spring 28 has a substantially V-shaped form in which the
application portion 26 and the clamping portion 30 are arranged at
an inclination to one another.
[0027] However, in the operating state, with the carbon brush 6
being installed, shown in FIG. 3, the application portion 26 is
pressed to the side in such a way that it lies substantially
parallel to the clamping portion 30. The tab portion 34 is
elastically deformed and now, as a result of elastic restoring
forces acting upon it, generates the supporting spring force SF
which acts on the carbon brush 6 by means of the application
portion 26.
[0028] To ensure that the carbon brush 6 is pressed against the
inclined guide surface 16 in a particularly uniform manner, the
application portion 26 has a length IB which can contact the carbon
brush 6 and which is at least 80% of a length IF of the guide
surface extending along the guide axis A.
[0029] Accordingly, over the lifetime of the carbon brush 6, this
carbon brush 6 is pressed increasingly into the taper 23 by the
supporting spring 28 as lateral wear on the contact surfaces K1 and
K2 increases. The carbon brush 6 is always guided in a stable
manner along the guide surface 16 directed parallel to the first
contact surface K2 and the holder side wall 20 which is directed
substantially parallel to the second contact surface K2.
Accordingly, when a sufficiently high supporting spring force SF is
applied, a tilting of the carbon brush 6 inside the carbon holder 4
can be prevented to a large extent even after a long operating
period and under strong vibrations.
[0030] Though the present invention was shown and described with
references to the preferred embodiment such is merely illustrative
of the present invention and is not to be construed as a limitation
thereof and various modifications of the present invention will be
apparent to those skilled in the art. It is therefore not intended
that the present invention be limited to the disclosed embodiment
or details thereof, and the present invention includes all
variations and/or alternative embodiments within the spirit and
scope of the present invention as defined by the appended
claims.
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